Such methods are used among others for drying compressed air.
Compressed air which is supplied for example by a compressor is in most cases saturated with water vapour or, in other words, has a relative humidity of 100%. This means that in case of a temperature drop below what is called the dew point, there will be condensation. The condensed water gives rise to corrosion in pipes and tools, and appliances may wear prematurely.
That is why compressed air is dried, which may be done in the above-mentioned manner by means of cool drying. Also other air than compressed air or other gases may be dried in this manner.
Cool drying is based on the principle that by lowering the air or gas temperature in the vaporizer, moisture in the air or gas will condense, after which the condensed water is separated in a liquid separator and after which the air or gas is heated again, such that this air or gas will be no longer saturated.
The same applies to any other gas than air, and each time we hereafter refer to air, the same also applies to any other gas than air.
A method for cool drying is already known, whereby on the basis of measurements of the vaporizer pressure or the vaporizer temperature, the cooling circuit is switched on or off.
If a take-off of compressed air is recorded, the cooling circuit is started and as soon as the take-off of compressed air stops again, the cooling circuit is stopped again as well.
A disadvantage of such a known method is that the heat exchanger, after the cooling circuit has been switched off, will heat up as there is no cooling any more.
When, subsequently, compressed air is taken off again while the heat exchanger is still relatively warm, temperature and dew point peaks may instantly occur in the supplied compressed air, since the gas to be dried in the heat exchanger is not sufficiently cooled then to make the water in said gas to be dried condense at maximum capacity.
A method for cool drying is known as well, whereby the cooling circuit stays operational at all times, also when there is no take-off of compressed air.
A major disadvantage of such a method is that it requires a considerable amount of energy, as the cooling circuit stays continuously operational, also in case of idle running.
A method for cool drying is also known whereby use is made of a thermal mass. With such a known method, use is made of an intermediary thermal mass, for example in the form of a mixture of water and propylene glycol, for cooling the compressed air.
Since the cooling circuit is only used for cooling the above-mentioned thermal mass, the compressor in this cooling circuit can be switched off as soon as the thermal mass has reached a certain temperature, such that energy can be saved.
A disadvantage of such a known method is that the cooling circuit, due to the presence of the above-mentioned thermal mass, must be made very heavy and sizeable.
Another disadvantage of such a known method is that, due to additional parts such as a reservoir and/or an additional heat exchanger, the construction of the cooling circuit is relatively expensive and complicated and its assembly is very time-consuming.